The present invention relates to a gas discharge display panel adapted for effecting display by means of a plurality of gas discharge elements arranged in a matrix, and also pertains to a cathode for use in such gas discharge display panel. More particularly, the present invention is concerned with a gas discharge display panel that employs as a cathode material rare earth hexaborides, known as substances which exhibit excellent electron emission characteristics, and also pertains to a cathode for use in such display panel.
This type of gas discharge display panel is disclosed in, e.g., U.S. Pat. No. 4,206,386. One example of conventional gas discharge display panels is shown in FIG. 1. As illustrated, this device has a two-electrode group structure in which a Y-direction electrode group K.sub.R, K.sub.1, K.sub.2, K.sub.3, K.sub.4, and K.sub.5 adapted to operate as cathode elements and an X-direction electrode group A.sub.1, A.sub.2, A.sub.3 and A.sub.4 adapted to operate as anode elements are provided between glass plates 1, 2 so that the two electrode groups extend orthogonally to each other. Relatively long and narrow strip-like dielectrics 16 are provided so as to extend parallel to respective anode elements, thereby partitioning the discharge space into individual discharge areas which are vacuum-sealed in a gas that emits light when an electric discharge occurs therein. Discharge dots 15 are respectively formed at intersections between the X-Y electrode elements.
It is strongly demanded to lower the driving voltage in such gas discharge display panel with the view to simplifying the driving circuit, reducing the costs and extending the lifetime of the panel itself.
The application of rare earth hexaborides, represented by LaB.sub.6, to cathode elements of a gas discharge display panel has already been practiced in DC discharge display panels, and it has been confirmed that rare earth hexaborides are effective in lowering the discharge maintenance voltage (see the Television Society Technical Report, ED-572 , 1981, or the specification of Japanese Patent Laid-Open No. 62647/1980). However, in these examples, LaB.sub.6 film is formed by plasma spray coating or thick film printing, and in these methods a polycrystalline film having irregular crystalline orientation is employed. In addition, LaB.sub.6 film may also be formed by electron beam heating (see the specification of Japanese Patent Publication No. 17780/1981). In this case, however, no consideration has heretofore been taken for the preference of a crystal plane of a film deposited by evaporation.
The discharge maintenance voltage in a gas discharge display panel can be made lower as the work function of the cathode thereof is decreased. However, the work function of rare earth hexaborides such as LaB.sub.6 greatly differs in accordance with the kind of crystal plane. Accordingly, conventionally employed LaB.sub.6 films, which are polycrystalline films or in which no consideration is taken for the preference of the crystal plane, have variations in discharge maintenance voltage and have not satisfactorily lowered the discharge maintenance voltage.